This we see from the fact that we understand the sense of the propositional sign, without having had it explained to us.
4.021 The proposition is a picture of reality, for I know the state of affaires presented by it, if I understand the proposition. And I understand the proposition, without its sense having been explained to me.
4.022 The proposition shows its sense.
The proposition shows how things stand, if it is true. And it says, that they do so stand.
4.023 The proposition determines reality to this extent, that one only needs to say "Yes" or "No" to it to make it agree with reality.
Reality must therefore be completely described by the proposition.
A proposition is the description of a fact.
As the description of an object describes it by its external properties so propositions describe reality by its internal properties.
The proposition constructs a world with the help of a logical scaffolding, and therefore one can actually see in the proposition all the logical features possessed by reality if it is true. One can draw conclusions from a false proposition.
4.024 To understand a proposition means to know what is the case, if it is true.
(One can therefore understand it without knowing whether it is true or not.)
One understands it if one understands it constituent parts.
4.025 The translation of one language into another is not a process of translating each proposition of the one into a proposition of the other, but only the constituent parts of propositions are translated.
(And the dictionary does not only translate substantives but also adverbs and conjunctions, etc., and it treats them all alike.)
4.026 The meanings of the simple signs (the words) must be explained to us, if we are to understand them.
By means of propositions we explain ourselves.
4.027 It is essential to propositions, that they can communicate a new sense to us.